Loss of body weight and a decline in nutritional status, is common in advanced AIDS and is associated with poor prognosis. Causes of weight loss in HIV infection include anorexia, poor oral intake, increased metabolic requirements or ineffective metabolism, and gastrointestinal dysfunction with malabsorption. While malnutrition has been studies in advanced HIV infection, relatively little is known about the nutritional changes in early HIV infection which lead to progressive malnutrition and weight loss. This project studies the influence of dietary intake, metabolic state, and gastrointestinal function in the development of weight loss, changes in body composition, and malnutrition in HIV infection. Emphasis is placed on nutritional events in early stages of infection. A cohort of HIV-infected persons will be followed for changes in clinical, nutritional and immunological status longitudinally every 6 months over a 3-year period. They will be stratified on admission into 3 groups based on CD4 counts, greater than 500,200-500 and less than 200. Recruitment of women and minorities will receive high priority. We will determine body composition, dietary intake, serum biochemical and immunologic tests, functional status and quality of life, along with tracking clinical progression of disease. In subsets of participants, gastrointestinal function and indirect calorimetry will be measured. Identifying the time course of nutritional changes and predictors of outcome will help in the design of early intervention with appropriate, targeted nutritional therapy. This, in turn, could improve quality of life, decrease the incidence of infections, and increase life-span for persons with HIV infection.